In recent years, biaxially drawn, blow molded bottles made of a polyester resin are in use as the containers for tea, juices, and other drinks. Among these bottles, polyethylene terephthalate resin bottles (hereinafter referred to as the PET bottles) are widely in use as the containers for drinks because the PET bottles have various advantages, including a high gas barrier property, high transparency, toughness that prevents bottles from being broken when they fall from some height, a non-adsorbing property that prevents the odor of the contents from being adsorbed to the bottle, and/or non-smelling property indicating that the bottles have no smell of themselves.
Carbonated drinks are put in pressure resistant PET bottles, such as described in Patent Document 1. The bottom of these bottles has plural projected feet and a so-called petaloid shape. FIG. 4 shows a representative example of the pressure resistant PET bottle. The bottle 101 comprises a neck 102, a shoulder 103, a cylindrical body 104, and a bottom 105 in a petaloid shape. This bottle is protected against deformation caused under a pressurized condition.
Meanwhile, in the applications requiring pasteurization at a high temperature, as in the cases of the drinks having a carbonate component, such as the carbonated drinks containing fruit juices, the bottles are filled with the contents and the neck of each bottle is closed with a cap by screw engagement. Then, the contents of the bottle are pasteurized with hot water shower at a temperature in the range of 60-70 deg C. During this operation, the bottle inside becomes highly pressurized at the high temperature, and a high pressure is placed on the bottom. Under this condition, there often occurs the so-called bottom sag, i.e., the deformation in the petaloid shaped bottom that can give damage to the ability of the bottle to stand upright.
Thus, the so-called heat and pressure resistant plastic bottles having pressure resistance at high temperatures are utilized for applications to carbonated drinks containing fruit juices. Patent Document 2 describes a bottle in which heat resistant property of the bottom has been improved by heat-treating the bottom and a nearby area to increase the degree of crystallization. Double blow-molded bottles described in Patent Document 3 can also be used as the heat and pressure resistant plastic bottles.    [Patent Document 1] Published patent application JP1995-267235    [Patent Document 2] Published patent application JP2001-150522    [Patent Document 3] Published examined patent application JP1995-67732